What are Mazda Miata Frankenstein Bolts?

Answer 1

Miata Frankenstein Bolts are hardtop posts available to all Miatas from 1990-2005. They are equipped on Miatas that have removable hardtops.

The Frankenstein bolts are mounted on the small chrome pieces near the upper corners of the trunk. The rear of the hardtop has two chrome covers that include bolts and shims that will tighten around the frankentstein bolts to secure the rear of the hardtop to the car.

If your Miata does not have them, they can purchased to replaced the two chrome bolts closest to the rear window on the chrome piece. While installing them with a Phillips head screwdriver, Loctite is recommended to ensure the bolts do not back out.

While not safe to do so, I have installed a hardtop without the Frankenstein bolts to see what would happen. Running only the front latches attached, I was able to drive around with minimal risk up to 60mph. Above 60mph, the generated air began lifting the rear of the hardtop in the air, creating a 1-2inch gap between the hardtop and the car.

Do so at your own risk, but if you want to purchase a hardtop, do not have the means to carry it by truck and do not have Frankenstein bolts, it is relatively safe to mount it to your Miata for transport at low speeds.